1. Field of the Invention
The present invention relates to a structure for a plasma processing chamber, a plasma processing chamber, a plasma processing apparatus, and a plasma processing chamber component, and more particularly to a structure for a plasma processing chamber and a plasma processing chamber component, which are exposed to plasma.
2. Description of the Related Art
Conventionally, there has been proposed a plasma processing chamber provided with a hollow cylindrical container, and electrodes that are disposed in the container and are connected to high-frequency power supplies, respectively. In the plasma processing chamber, a process gas is introduced into the container, and electrodes apply high-frequency power to a space within the container. Further, when a semiconductor wafer as a substrate is received in the container, the introduced process gas is turned into a plasma by the high-frequency power to generate ions and the like, whereby the semiconductor wafer is subjected to plasma processing, such as etching, by the ions and the like.
When a reactive gas, such as a mixed gas comprised of a C4F8 gas and an argon (Ar) gas, is used as a process gas, depositable active species (radicals) generated from the reactive gas are deposited as polymer on the inner sidewall (hereinafter simply referred to as “the sidewall”) of the container. If the amount of deposited polymer is too large, the polymer can be exfoliated from the sidewall when plasma processing is performed on the semiconductor wafer to be attached to the surface thereof as deposits, and hence it is required to remove the polymer deposited on the sidewall.
It is preferred that the polymer deposited on the sidewall is removed by causing positive ions generated when the process gas is turned into the plasma, to collide against the sidewall. The number of times of collision of positive ions against the sidewall depends on the potential of the sidewall. More specifically, when the potential of the sidewall is low, and hence the potential difference between the sidewall and the plasma generated from the process gas in the space within the processing chamber is large, the number of times of collision of positive ions against the sidewall increases to remove the deposited polymer.
However, in a type of processing in which depositable active species are not generated (i.e. deposition-free processing), such as a process in which an O2 gas is used as a process gas, when the potential difference between the sidewall and the plasma is too large, the number of times of collision of positive ions against the sidewall becomes so large as to sometimes shave not only the deposited polymer but also the sidewall. Therefore, it is required to control the potential of the sidewall, to thereby appropriately adjust the number of times of collision of positive ions against the sidewall.
As a technique of controlling the potential of the sidewall of the plasma processing chamber, a method is known in which the anode/cathode ratio of the container in the plasma processing chamber is adjusted. The anode/cathode ratio of the container varies with the distance (gap) between an upper electrode and a lower electrode disposed in the container and the position of an exhaust plate disposed in the same. Therefore, in order to adjust the anode/cathode ratio, it is required to change the gap and/or the position of the exhaust plate, which can hinder the distribution of plasma density and the like in the container from being set preferably for etching.
To overcome the problem, as a technique of controlling the potential of the sidewall of the plasma processing chamber without adjusting the anode/cathode ratio of the container, it has been proposed to dispose a potential control circuit provided with an impedance adjusting means, such as variable capacitors and coils, between the sidewall and a ground potential, and control the potential of the sidewall by adjusting the impedance of the potential control circuit (see e.g. Japanese Laid-Open Patent Publication (Kokai) Nos. H10-275694 and H11-176821).
Further, since polymer is sometimes deposited not only on the sidewall but also on the surfaces of the electrodes, or the electrodes are sometimes shaved by positive ions, it is preferable to dispose a potential control circuit provided with an impedance adjusting means between the electrodes and the ground potential, thereby controlling the potential of the electrodes.
According to the above-described technique of controlling the potential, however, the potential control circuit provided with the impedance adjusting means is required, which makes the construction of the plasma processing chamber complicated. This also causes an increase in manufacturing costs of the plasma processing chamber.
Further, the above described technique is only capable of controlling the potential of the sidewall uniformly. However, the amount of deposition of polymer is not uniform throughout the plasma processing chamber, which makes it impossible to properly remove the polymer.